The Applicant has refined the approved EP patent for Strömdahl relating to a coaxial coupling, published approval in European Patent Gazette 02.10.85 Bulletin 85/40 (publication number EP 0 074 991 B1).
One object of Strömdahl's coaxial coupling is to produce a coaxial hose coupling for a coaxial hose, which allows one coupling half, which at the time of connection is coupled to a pressure-generating pump or compressor, to be rapidly connected up to the other coupling half by manual means.
The structure of the coaxial coupling allows free rotation of one coupling half in relation to the other one.
Another object of Strömdahl's construction is to produce a coaxial coupling, the component parts of which are of simple construction from the production engineering aspect, comprising simple compression springs and substantially rotationally symmetrical parts with cylindrical and conical faces with common principal axis and flat faces.
GB 2 069 083 shows a male part which must be rotated relative to a female part in order to disconnect the coupling. A safety sleeve with L-shaped grooves is fastened to the female part, by means of which grooves the male part is locked in place. The safety sleeve serves to prevent the male part from uncontrolledly flying out of the female part due to excess pressure in the female part.
U.S. Pat. No. 647,299 shows a coupling having a male part with pins, which are rotated in bayonet grooves in a locking sleeve fastened in the female part in order to bring the two coupling parts together. Locking spikes are decoupled from the male part by means of a predetermined axial force upon the coupling parts, so that the male part can rotate out of the female part.
GB 541842 shows a one-way coupling having a male part comprising a non-return valve for pressurized air. A bayonet coupling is designed to bring the two coupling parts together. The female part has a fastened guide sleeve with grooves for a bayonet coupling and the male part has pins. In the connection, the whole of the female part with valve seat is screwed onto the male part.
A drawback with known coaxial couplings is that, if a cold hydraulic tool with nipple (not coupled together with the coupling) is left in the sun, then this is warmed up. The hydraulic oil in the nipple expands and the enclosed pressure increases. This pressure can be up to a few hundred bar, which makes coupling together impossible without the use of a special tool to “emergency open” some valve and discharge the pressure into the open air. This can adversely affect the rescue work.
A further drawback with known coaxial couplings is that, since the coupling (the female part) is pressurized, when a pressurizing pump is connected to the female part, a rapid-action coupling together is made impossible without a large force having to be manually applied. This can result in a large number of persons having to join forces, which is inefficient in a motor vehicle accident, for example, and in cutting tools having to be connected up. The drawback is therefore that one cannot manage to force the coaxial coupling together like a traditional rapid-action coupling.
There is therefore a desire to improve the working efficiency at the site of an accident.